1. Field of the Invention
The present invention relates to metal detectors. More specifically, the present invention relates to a hand-held metal detector having an excavation tool.
2. Description of the Related Art
Metal detectors have been widely used for hobby, commercial, and security application for many decades. The modern metal detector consists of one or more search coils coupled to a detector circuit, which in turn, is connected to a user interface that reports the detection and presence of metallic objects to the operator. The search coil(s) establishes an electromagnetic field, called a search field, which can effectively penetrate non-metallic materials, such as soil, water and other materials. When the search field is moved into proximity of a metallic object, the field is disturbed and the detector circuit senses this disturbance. Those skilled in the art are familiar with a number of field establishing and field disturbance detecting techniques, which can be used to estimate the size, location, and the content of the metallic objects in question. There are certain correlations between the search field and the search coil. Generally, a larger coil produces a larger field, and this enables deeper penetration by the field. However, there is a trade-off in that a larger search field provides a less accurate determination of the specific location of the target metallic object. Specialized coils have been devised that yield uniquely shaped search fields in an attempt to achieve deep penetration and accurate location. Nonetheless, a performance trade off exists between field penetration and metallic object location accuracy.
A common application for metal detectors is treasure hunting by hobbyists. Desirable target metallic objects sought by hobbyists are coins, jewelry, artifacts, and other treasure, for example. Given a relatively large search area, such as a public park for example, hobbyists will typically select a ground search metal detector that is effective for sweeping, or scanning, a large area with good field search field penetration depth. Good penetration for small objects would be approximately six to twelve inches. A ground search metal detector typically employs a relatively large search coil (perhaps six to twelve inches in diameter) that is sequentially scanned back and forth, about one or two inches above the ground surface. To facilitate the user interface, a stem is usually employed to support the search coil and reach upwardly to a comfortable height for the user to carry the metal detector while standing and scanning the ground. The stem also supports the detector circuit and user interface at a comfortable position, and may include various handles and arm rests for user comfort.
During a treasure hunt using a ground search metal detector, a fortunate hobbyist may receive and alert from the metal detector indicating that a metallic object has been located. The next step is to dig into the soil and retrieve the treasure. Off course, many times it is not real treasure, but merely other metallic debris, such as bottle caps, foils wads and so forth. Thus, treasure hunting with a metal detector is a repetitive task. As a practical matter, it is not necessarily easy or trivial to retrieve the metallic object discovered using a ground search metal detector. The user is faced with the task of digging a six to twelve in hole that is six to twelve inches deep for each alert that the metal detector provides. This issue has been alleviated to a certain degree through utilization of a second smaller coil or even a second metal detector that has a much smaller detection coil to scan the area identified by the larger coil on the ground search metal detector. This procedure is helpful to a degree, however, the smaller coil will not penetrate as deeply, so the user may have to scan, then dig, then scan again, etc. etc. Additionally, a typical user will not dig into the soil with his bare hands, but rather carry some sort of tool to assist in the digging operation. The user may have a ground search detector, a smaller detector, and one or more digging tools to manage during a treasure hunt. Thus it can be appreciated that there is a need in the art for an apparatus and method to assist a metal detector user in locating and retrieving a metallic objects that are concealed in soil or other material.